Doctors found cartilage damage during an exploratory procedure, and team physician Dr. Don Roberts performed microfracture surgery to repair the damage.

"There are things about this that are positive for Greg. First of all, he is young. The area where the damage was is small and the rest of his knee looked normal," Roberts said in a statement. "All those are good signs for a complete recovery from microfracture surgery."

Oden

The 7-foot center is expected to be on crutches for up to eight weeks. Full recovery likely will take six to 12 months, the team said.

Oden was the No. 1 pick in the June draft out of Ohio State, where he averaged 15.7 points and 9.6 rebounds.

"Certainly this is a setback, but our future is still incredibly bright," Trail Blazers general manager Kevin Pritchard said. "Is it disappointing? Yes. However, this is a great core of talent and players of strong character and will continue to be."

It was Oden's second health problem since the Trail Blazers drafted him. He had a tonsillectomy in July after struggling in two Las Vegas summer league games.

Oden recovered and had been working out in the Portland area. The MRI was taken Thursday, and Oden refrained from working out over the weekend.

Despite being hampered by a wrist injury at Ohio State, Oden led the Buckeyes to the national championship game as a freshman. He had 25 points and 12 rebounds in the loss to Florida.

Oden talked about the injury earlier this week in his blog. He said he had a sharp pain about a month ago when he was on vacation.

"I didn't tell anyone because I didn't want to seem like I was complaining or making excuses for anything. Plus I wasn't doing anything at the time I realized it hurt, so I figured it couldn't be anything big," he said.

The Blazers open training camp Oct. 2. The regular season opener is at San Antonio on Oct. 30.